1/*
   2 * random.c -- A strong random number generator
   3 *
 
 
 
   4 * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005
   5 *
   6 * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999.  All
   7 * rights reserved.
   8 *
   9 * Redistribution and use in source and binary forms, with or without
  10 * modification, are permitted provided that the following conditions
  11 * are met:
  12 * 1. Redistributions of source code must retain the above copyright
  13 *    notice, and the entire permission notice in its entirety,
  14 *    including the disclaimer of warranties.
  15 * 2. Redistributions in binary form must reproduce the above copyright
  16 *    notice, this list of conditions and the following disclaimer in the
  17 *    documentation and/or other materials provided with the distribution.
  18 * 3. The name of the author may not be used to endorse or promote
  19 *    products derived from this software without specific prior
  20 *    written permission.
  21 *
  22 * ALTERNATIVELY, this product may be distributed under the terms of
  23 * the GNU General Public License, in which case the provisions of the GPL are
  24 * required INSTEAD OF the above restrictions.  (This clause is
  25 * necessary due to a potential bad interaction between the GPL and
  26 * the restrictions contained in a BSD-style copyright.)
  27 *
  28 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
  29 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  30 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
  31 * WHICH ARE HEREBY DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE
  32 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  33 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
  34 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
  35 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  36 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
  38 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
  39 * DAMAGE.
  40 */
  41
  42/*
  43 * (now, with legal B.S. out of the way.....)
  44 *
  45 * This routine gathers environmental noise from device drivers, etc.,
  46 * and returns good random numbers, suitable for cryptographic use.
  47 * Besides the obvious cryptographic uses, these numbers are also good
  48 * for seeding TCP sequence numbers, and other places where it is
  49 * desirable to have numbers which are not only random, but hard to
  50 * predict by an attacker.
  51 *
  52 * Theory of operation
  53 * ===================
  54 *
  55 * Computers are very predictable devices.  Hence it is extremely hard
  56 * to produce truly random numbers on a computer --- as opposed to
  57 * pseudo-random numbers, which can easily generated by using a
  58 * algorithm.  Unfortunately, it is very easy for attackers to guess
  59 * the sequence of pseudo-random number generators, and for some
  60 * applications this is not acceptable.  So instead, we must try to
  61 * gather "environmental noise" from the computer's environment, which
  62 * must be hard for outside attackers to observe, and use that to
  63 * generate random numbers.  In a Unix environment, this is best done
  64 * from inside the kernel.
  65 *
  66 * Sources of randomness from the environment include inter-keyboard
  67 * timings, inter-interrupt timings from some interrupts, and other
  68 * events which are both (a) non-deterministic and (b) hard for an
  69 * outside observer to measure.  Randomness from these sources are
  70 * added to an "entropy pool", which is mixed using a CRC-like function.
  71 * This is not cryptographically strong, but it is adequate assuming
  72 * the randomness is not chosen maliciously, and it is fast enough that
  73 * the overhead of doing it on every interrupt is very reasonable.
  74 * As random bytes are mixed into the entropy pool, the routines keep
  75 * an *estimate* of how many bits of randomness have been stored into
  76 * the random number generator's internal state.
  77 *
  78 * When random bytes are desired, they are obtained by taking the SHA
  79 * hash of the contents of the "entropy pool".  The SHA hash avoids
  80 * exposing the internal state of the entropy pool.  It is believed to
  81 * be computationally infeasible to derive any useful information
  82 * about the input of SHA from its output.  Even if it is possible to
  83 * analyze SHA in some clever way, as long as the amount of data
  84 * returned from the generator is less than the inherent entropy in
  85 * the pool, the output data is totally unpredictable.  For this
  86 * reason, the routine decreases its internal estimate of how many
  87 * bits of "true randomness" are contained in the entropy pool as it
  88 * outputs random numbers.
  89 *
  90 * If this estimate goes to zero, the routine can still generate
  91 * random numbers; however, an attacker may (at least in theory) be
  92 * able to infer the future output of the generator from prior
  93 * outputs.  This requires successful cryptanalysis of SHA, which is
  94 * not believed to be feasible, but there is a remote possibility.
  95 * Nonetheless, these numbers should be useful for the vast majority
  96 * of purposes.
  97 *
  98 * Exported interfaces ---- output
  99 * ===============================
 100 *
 101 * There are three exported interfaces; the first is one designed to
 102 * be used from within the kernel:
 103 *
 104 * 	void get_random_bytes(void *buf, int nbytes);
 105 *
 106 * This interface will return the requested number of random bytes,
 107 * and place it in the requested buffer.
 108 *
 109 * The two other interfaces are two character devices /dev/random and
 110 * /dev/urandom.  /dev/random is suitable for use when very high
 111 * quality randomness is desired (for example, for key generation or
 112 * one-time pads), as it will only return a maximum of the number of
 113 * bits of randomness (as estimated by the random number generator)
 114 * contained in the entropy pool.
 115 *
 116 * The /dev/urandom device does not have this limit, and will return
 117 * as many bytes as are requested.  As more and more random bytes are
 118 * requested without giving time for the entropy pool to recharge,
 119 * this will result in random numbers that are merely cryptographically
 120 * strong.  For many applications, however, this is acceptable.
 121 *
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 122 * Exported interfaces ---- input
 123 * ==============================
 124 *
 125 * The current exported interfaces for gathering environmental noise
 126 * from the devices are:
 127 *
 128 *	void add_device_randomness(const void *buf, unsigned int size);
 129 * 	void add_input_randomness(unsigned int type, unsigned int code,
 130 *                                unsigned int value);
 131 *	void add_interrupt_randomness(int irq, int irq_flags);
 132 * 	void add_disk_randomness(struct gendisk *disk);
 133 *
 134 * add_device_randomness() is for adding data to the random pool that
 135 * is likely to differ between two devices (or possibly even per boot).
 136 * This would be things like MAC addresses or serial numbers, or the
 137 * read-out of the RTC. This does *not* add any actual entropy to the
 138 * pool, but it initializes the pool to different values for devices
 139 * that might otherwise be identical and have very little entropy
 140 * available to them (particularly common in the embedded world).
 141 *
 142 * add_input_randomness() uses the input layer interrupt timing, as well as
 143 * the event type information from the hardware.
 144 *
 145 * add_interrupt_randomness() uses the interrupt timing as random
 146 * inputs to the entropy pool. Using the cycle counters and the irq source
 147 * as inputs, it feeds the randomness roughly once a second.
 148 *
 149 * add_disk_randomness() uses what amounts to the seek time of block
 150 * layer request events, on a per-disk_devt basis, as input to the
 151 * entropy pool. Note that high-speed solid state drives with very low
 152 * seek times do not make for good sources of entropy, as their seek
 153 * times are usually fairly consistent.
 154 *
 155 * All of these routines try to estimate how many bits of randomness a
 156 * particular randomness source.  They do this by keeping track of the
 157 * first and second order deltas of the event timings.
 158 *
 159 * Ensuring unpredictability at system startup
 160 * ============================================
 161 *
 162 * When any operating system starts up, it will go through a sequence
 163 * of actions that are fairly predictable by an adversary, especially
 164 * if the start-up does not involve interaction with a human operator.
 165 * This reduces the actual number of bits of unpredictability in the
 166 * entropy pool below the value in entropy_count.  In order to
 167 * counteract this effect, it helps to carry information in the
 168 * entropy pool across shut-downs and start-ups.  To do this, put the
 169 * following lines an appropriate script which is run during the boot
 170 * sequence:
 171 *
 172 *	echo "Initializing random number generator..."
 173 *	random_seed=/var/run/random-seed
 174 *	# Carry a random seed from start-up to start-up
 175 *	# Load and then save the whole entropy pool
 176 *	if [ -f $random_seed ]; then
 177 *		cat $random_seed >/dev/urandom
 178 *	else
 179 *		touch $random_seed
 180 *	fi
 181 *	chmod 600 $random_seed
 182 *	dd if=/dev/urandom of=$random_seed count=1 bs=512
 183 *
 184 * and the following lines in an appropriate script which is run as
 185 * the system is shutdown:
 186 *
 187 *	# Carry a random seed from shut-down to start-up
 188 *	# Save the whole entropy pool
 189 *	echo "Saving random seed..."
 190 *	random_seed=/var/run/random-seed
 191 *	touch $random_seed
 192 *	chmod 600 $random_seed
 193 *	dd if=/dev/urandom of=$random_seed count=1 bs=512
 194 *
 195 * For example, on most modern systems using the System V init
 196 * scripts, such code fragments would be found in
 197 * /etc/rc.d/init.d/random.  On older Linux systems, the correct script
 198 * location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0.
 199 *
 200 * Effectively, these commands cause the contents of the entropy pool
 201 * to be saved at shut-down time and reloaded into the entropy pool at
 202 * start-up.  (The 'dd' in the addition to the bootup script is to
 203 * make sure that /etc/random-seed is different for every start-up,
 204 * even if the system crashes without executing rc.0.)  Even with
 205 * complete knowledge of the start-up activities, predicting the state
 206 * of the entropy pool requires knowledge of the previous history of
 207 * the system.
 208 *
 209 * Configuring the /dev/random driver under Linux
 210 * ==============================================
 211 *
 212 * The /dev/random driver under Linux uses minor numbers 8 and 9 of
 213 * the /dev/mem major number (#1).  So if your system does not have
 214 * /dev/random and /dev/urandom created already, they can be created
 215 * by using the commands:
 216 *
 217 * 	mknod /dev/random c 1 8
 218 * 	mknod /dev/urandom c 1 9
 219 *
 220 * Acknowledgements:
 221 * =================
 222 *
 223 * Ideas for constructing this random number generator were derived
 224 * from Pretty Good Privacy's random number generator, and from private
 225 * discussions with Phil Karn.  Colin Plumb provided a faster random
 226 * number generator, which speed up the mixing function of the entropy
 227 * pool, taken from PGPfone.  Dale Worley has also contributed many
 228 * useful ideas and suggestions to improve this driver.
 229 *
 230 * Any flaws in the design are solely my responsibility, and should
 231 * not be attributed to the Phil, Colin, or any of authors of PGP.
 232 *
 233 * Further background information on this topic may be obtained from
 234 * RFC 1750, "Randomness Recommendations for Security", by Donald
 235 * Eastlake, Steve Crocker, and Jeff Schiller.
 236 */
 237
 238#include <linux/utsname.h>
 239#include <linux/module.h>
 240#include <linux/kernel.h>
 241#include <linux/major.h>
 242#include <linux/string.h>
 243#include <linux/fcntl.h>
 244#include <linux/slab.h>
 245#include <linux/random.h>
 246#include <linux/poll.h>
 247#include <linux/init.h>
 248#include <linux/fs.h>
 249#include <linux/genhd.h>
 250#include <linux/interrupt.h>
 251#include <linux/mm.h>
 
 252#include <linux/spinlock.h>
 253#include <linux/kthread.h>
 254#include <linux/percpu.h>
 255#include <linux/cryptohash.h>
 256#include <linux/fips.h>
 257#include <linux/ptrace.h>
 258#include <linux/kmemcheck.h>
 259#include <linux/workqueue.h>
 260#include <linux/irq.h>
 
 261#include <linux/syscalls.h>
 262#include <linux/completion.h>
 
 
 263
 264#include <asm/processor.h>
 265#include <asm/uaccess.h>
 266#include <asm/irq.h>
 267#include <asm/irq_regs.h>
 268#include <asm/io.h>
 269
 270#define CREATE_TRACE_POINTS
 271#include <trace/events/random.h>
 272
 273/* #define ADD_INTERRUPT_BENCH */
 274
 275/*
 276 * Configuration information
 277 */
 278#define INPUT_POOL_SHIFT	12
 279#define INPUT_POOL_WORDS	(1 << (INPUT_POOL_SHIFT-5))
 280#define OUTPUT_POOL_SHIFT	10
 281#define OUTPUT_POOL_WORDS	(1 << (OUTPUT_POOL_SHIFT-5))
 282#define SEC_XFER_SIZE		512
 283#define EXTRACT_SIZE		10
 284
 285#define DEBUG_RANDOM_BOOT 0
 286
 287#define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
 288
 289/*
 290 * To allow fractional bits to be tracked, the entropy_count field is
 291 * denominated in units of 1/8th bits.
 292 *
 293 * 2*(ENTROPY_SHIFT + log2(poolbits)) must <= 31, or the multiply in
 294 * credit_entropy_bits() needs to be 64 bits wide.
 295 */
 296#define ENTROPY_SHIFT 3
 297#define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT)
 298
 299/*
 300 * The minimum number of bits of entropy before we wake up a read on
 301 * /dev/random.  Should be enough to do a significant reseed.
 302 */
 303static int random_read_wakeup_bits = 64;
 304
 305/*
 306 * If the entropy count falls under this number of bits, then we
 307 * should wake up processes which are selecting or polling on write
 308 * access to /dev/random.
 309 */
 310static int random_write_wakeup_bits = 28 * OUTPUT_POOL_WORDS;
 311
 312/*
 313 * The minimum number of seconds between urandom pool reseeding.  We
 314 * do this to limit the amount of entropy that can be drained from the
 315 * input pool even if there are heavy demands on /dev/urandom.
 316 */
 317static int random_min_urandom_seed = 60;
 318
 319/*
 320 * Originally, we used a primitive polynomial of degree .poolwords
 321 * over GF(2).  The taps for various sizes are defined below.  They
 322 * were chosen to be evenly spaced except for the last tap, which is 1
 323 * to get the twisting happening as fast as possible.
 324 *
 325 * For the purposes of better mixing, we use the CRC-32 polynomial as
 326 * well to make a (modified) twisted Generalized Feedback Shift
 327 * Register.  (See M. Matsumoto & Y. Kurita, 1992.  Twisted GFSR
 328 * generators.  ACM Transactions on Modeling and Computer Simulation
 329 * 2(3):179-194.  Also see M. Matsumoto & Y. Kurita, 1994.  Twisted
 330 * GFSR generators II.  ACM Transactions on Modeling and Computer
 331 * Simulation 4:254-266)
 332 *
 333 * Thanks to Colin Plumb for suggesting this.
 334 *
 335 * The mixing operation is much less sensitive than the output hash,
 336 * where we use SHA-1.  All that we want of mixing operation is that
 337 * it be a good non-cryptographic hash; i.e. it not produce collisions
 338 * when fed "random" data of the sort we expect to see.  As long as
 339 * the pool state differs for different inputs, we have preserved the
 340 * input entropy and done a good job.  The fact that an intelligent
 341 * attacker can construct inputs that will produce controlled
 342 * alterations to the pool's state is not important because we don't
 343 * consider such inputs to contribute any randomness.  The only
 344 * property we need with respect to them is that the attacker can't
 345 * increase his/her knowledge of the pool's state.  Since all
 346 * additions are reversible (knowing the final state and the input,
 347 * you can reconstruct the initial state), if an attacker has any
 348 * uncertainty about the initial state, he/she can only shuffle that
 349 * uncertainty about, but never cause any collisions (which would
 350 * decrease the uncertainty).
 351 *
 352 * Our mixing functions were analyzed by Lacharme, Roeck, Strubel, and
 353 * Videau in their paper, "The Linux Pseudorandom Number Generator
 354 * Revisited" (see: http://eprint.iacr.org/2012/251.pdf).  In their
 355 * paper, they point out that we are not using a true Twisted GFSR,
 356 * since Matsumoto & Kurita used a trinomial feedback polynomial (that
 357 * is, with only three taps, instead of the six that we are using).
 358 * As a result, the resulting polynomial is neither primitive nor
 359 * irreducible, and hence does not have a maximal period over
 360 * GF(2**32).  They suggest a slight change to the generator
 361 * polynomial which improves the resulting TGFSR polynomial to be
 362 * irreducible, which we have made here.
 363 */
 364static struct poolinfo {
 365	int poolbitshift, poolwords, poolbytes, poolbits, poolfracbits;
 366#define S(x) ilog2(x)+5, (x), (x)*4, (x)*32, (x) << (ENTROPY_SHIFT+5)
 367	int tap1, tap2, tap3, tap4, tap5;
 368} poolinfo_table[] = {
 369	/* was: x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 */
 370	/* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */
 371	{ S(128),	104,	76,	51,	25,	1 },
 372	/* was: x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 */
 373	/* x^32 + x^26 + x^19 + x^14 + x^7 + x + 1 */
 374	{ S(32),	26,	19,	14,	7,	1 },
 375#if 0
 376	/* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1  -- 115 */
 377	{ S(2048),	1638,	1231,	819,	411,	1 },
 378
 379	/* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
 380	{ S(1024),	817,	615,	412,	204,	1 },
 381
 382	/* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
 383	{ S(1024),	819,	616,	410,	207,	2 },
 384
 385	/* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
 386	{ S(512),	411,	308,	208,	104,	1 },
 387
 388	/* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
 389	{ S(512),	409,	307,	206,	102,	2 },
 390	/* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
 391	{ S(512),	409,	309,	205,	103,	2 },
 392
 393	/* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
 394	{ S(256),	205,	155,	101,	52,	1 },
 395
 396	/* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
 397	{ S(128),	103,	78,	51,	27,	2 },
 398
 399	/* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
 400	{ S(64),	52,	39,	26,	14,	1 },
 401#endif
 402};
 403
 404/*
 405 * Static global variables
 406 */
 407static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
 408static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
 409static DECLARE_WAIT_QUEUE_HEAD(urandom_init_wait);
 410static struct fasync_struct *fasync;
 411
 412static DEFINE_SPINLOCK(random_ready_list_lock);
 413static LIST_HEAD(random_ready_list);
 414
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 415/**********************************************************************
 416 *
 417 * OS independent entropy store.   Here are the functions which handle
 418 * storing entropy in an entropy pool.
 419 *
 420 **********************************************************************/
 421
 422struct entropy_store;
 423struct entropy_store {
 424	/* read-only data: */
 425	const struct poolinfo *poolinfo;
 426	__u32 *pool;
 427	const char *name;
 428	struct entropy_store *pull;
 429	struct work_struct push_work;
 430
 431	/* read-write data: */
 432	unsigned long last_pulled;
 433	spinlock_t lock;
 434	unsigned short add_ptr;
 435	unsigned short input_rotate;
 436	int entropy_count;
 437	int entropy_total;
 438	unsigned int initialized:1;
 439	unsigned int limit:1;
 440	unsigned int last_data_init:1;
 441	__u8 last_data[EXTRACT_SIZE];
 442};
 443
 
 
 
 
 
 
 444static void push_to_pool(struct work_struct *work);
 445static __u32 input_pool_data[INPUT_POOL_WORDS];
 446static __u32 blocking_pool_data[OUTPUT_POOL_WORDS];
 447static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS];
 448
 449static struct entropy_store input_pool = {
 450	.poolinfo = &poolinfo_table[0],
 451	.name = "input",
 452	.limit = 1,
 453	.lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
 454	.pool = input_pool_data
 455};
 456
 457static struct entropy_store blocking_pool = {
 458	.poolinfo = &poolinfo_table[1],
 459	.name = "blocking",
 460	.limit = 1,
 461	.pull = &input_pool,
 462	.lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock),
 463	.pool = blocking_pool_data,
 464	.push_work = __WORK_INITIALIZER(blocking_pool.push_work,
 465					push_to_pool),
 466};
 467
 468static struct entropy_store nonblocking_pool = {
 469	.poolinfo = &poolinfo_table[1],
 470	.name = "nonblocking",
 471	.pull = &input_pool,
 472	.lock = __SPIN_LOCK_UNLOCKED(nonblocking_pool.lock),
 473	.pool = nonblocking_pool_data,
 474	.push_work = __WORK_INITIALIZER(nonblocking_pool.push_work,
 475					push_to_pool),
 476};
 477
 478static __u32 const twist_table[8] = {
 479	0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
 480	0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
 481
 482/*
 483 * This function adds bytes into the entropy "pool".  It does not
 484 * update the entropy estimate.  The caller should call
 485 * credit_entropy_bits if this is appropriate.
 486 *
 487 * The pool is stirred with a primitive polynomial of the appropriate
 488 * degree, and then twisted.  We twist by three bits at a time because
 489 * it's cheap to do so and helps slightly in the expected case where
 490 * the entropy is concentrated in the low-order bits.
 491 */
 492static void _mix_pool_bytes(struct entropy_store *r, const void *in,
 493			    int nbytes)
 494{
 495	unsigned long i, tap1, tap2, tap3, tap4, tap5;
 496	int input_rotate;
 497	int wordmask = r->poolinfo->poolwords - 1;
 498	const char *bytes = in;
 499	__u32 w;
 500
 501	tap1 = r->poolinfo->tap1;
 502	tap2 = r->poolinfo->tap2;
 503	tap3 = r->poolinfo->tap3;
 504	tap4 = r->poolinfo->tap4;
 505	tap5 = r->poolinfo->tap5;
 506
 507	input_rotate = r->input_rotate;
 508	i = r->add_ptr;
 509
 510	/* mix one byte at a time to simplify size handling and churn faster */
 511	while (nbytes--) {
 512		w = rol32(*bytes++, input_rotate);
 513		i = (i - 1) & wordmask;
 514
 515		/* XOR in the various taps */
 516		w ^= r->pool[i];
 517		w ^= r->pool[(i + tap1) & wordmask];
 518		w ^= r->pool[(i + tap2) & wordmask];
 519		w ^= r->pool[(i + tap3) & wordmask];
 520		w ^= r->pool[(i + tap4) & wordmask];
 521		w ^= r->pool[(i + tap5) & wordmask];
 522
 523		/* Mix the result back in with a twist */
 524		r->pool[i] = (w >> 3) ^ twist_table[w & 7];
 525
 526		/*
 527		 * Normally, we add 7 bits of rotation to the pool.
 528		 * At the beginning of the pool, add an extra 7 bits
 529		 * rotation, so that successive passes spread the
 530		 * input bits across the pool evenly.
 531		 */
 532		input_rotate = (input_rotate + (i ? 7 : 14)) & 31;
 533	}
 534
 535	r->input_rotate = input_rotate;
 536	r->add_ptr = i;
 537}
 538
 539static void __mix_pool_bytes(struct entropy_store *r, const void *in,
 540			     int nbytes)
 541{
 542	trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
 543	_mix_pool_bytes(r, in, nbytes);
 544}
 545
 546static void mix_pool_bytes(struct entropy_store *r, const void *in,
 547			   int nbytes)
 548{
 549	unsigned long flags;
 550
 551	trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
 552	spin_lock_irqsave(&r->lock, flags);
 553	_mix_pool_bytes(r, in, nbytes);
 554	spin_unlock_irqrestore(&r->lock, flags);
 555}
 556
 557struct fast_pool {
 558	__u32		pool[4];
 559	unsigned long	last;
 560	unsigned short	reg_idx;
 561	unsigned char	count;
 562};
 563
 564/*
 565 * This is a fast mixing routine used by the interrupt randomness
 566 * collector.  It's hardcoded for an 128 bit pool and assumes that any
 567 * locks that might be needed are taken by the caller.
 568 */
 569static void fast_mix(struct fast_pool *f)
 570{
 571	__u32 a = f->pool[0],	b = f->pool[1];
 572	__u32 c = f->pool[2],	d = f->pool[3];
 573
 574	a += b;			c += d;
 575	b = rol32(b, 6);	d = rol32(d, 27);
 576	d ^= a;			b ^= c;
 577
 578	a += b;			c += d;
 579	b = rol32(b, 16);	d = rol32(d, 14);
 580	d ^= a;			b ^= c;
 581
 582	a += b;			c += d;
 583	b = rol32(b, 6);	d = rol32(d, 27);
 584	d ^= a;			b ^= c;
 585
 586	a += b;			c += d;
 587	b = rol32(b, 16);	d = rol32(d, 14);
 588	d ^= a;			b ^= c;
 589
 590	f->pool[0] = a;  f->pool[1] = b;
 591	f->pool[2] = c;  f->pool[3] = d;
 592	f->count++;
 593}
 594
 595static void process_random_ready_list(void)
 596{
 597	unsigned long flags;
 598	struct random_ready_callback *rdy, *tmp;
 599
 600	spin_lock_irqsave(&random_ready_list_lock, flags);
 601	list_for_each_entry_safe(rdy, tmp, &random_ready_list, list) {
 602		struct module *owner = rdy->owner;
 603
 604		list_del_init(&rdy->list);
 605		rdy->func(rdy);
 606		module_put(owner);
 607	}
 608	spin_unlock_irqrestore(&random_ready_list_lock, flags);
 609}
 610
 611/*
 612 * Credit (or debit) the entropy store with n bits of entropy.
 613 * Use credit_entropy_bits_safe() if the value comes from userspace
 614 * or otherwise should be checked for extreme values.
 615 */
 616static void credit_entropy_bits(struct entropy_store *r, int nbits)
 617{
 618	int entropy_count, orig;
 619	const int pool_size = r->poolinfo->poolfracbits;
 620	int nfrac = nbits << ENTROPY_SHIFT;
 621
 622	if (!nbits)
 623		return;
 624
 625retry:
 626	entropy_count = orig = ACCESS_ONCE(r->entropy_count);
 627	if (nfrac < 0) {
 628		/* Debit */
 629		entropy_count += nfrac;
 630	} else {
 631		/*
 632		 * Credit: we have to account for the possibility of
 633		 * overwriting already present entropy.	 Even in the
 634		 * ideal case of pure Shannon entropy, new contributions
 635		 * approach the full value asymptotically:
 636		 *
 637		 * entropy <- entropy + (pool_size - entropy) *
 638		 *	(1 - exp(-add_entropy/pool_size))
 639		 *
 640		 * For add_entropy <= pool_size/2 then
 641		 * (1 - exp(-add_entropy/pool_size)) >=
 642		 *    (add_entropy/pool_size)*0.7869...
 643		 * so we can approximate the exponential with
 644		 * 3/4*add_entropy/pool_size and still be on the
 645		 * safe side by adding at most pool_size/2 at a time.
 646		 *
 647		 * The use of pool_size-2 in the while statement is to
 648		 * prevent rounding artifacts from making the loop
 649		 * arbitrarily long; this limits the loop to log2(pool_size)*2
 650		 * turns no matter how large nbits is.
 651		 */
 652		int pnfrac = nfrac;
 653		const int s = r->poolinfo->poolbitshift + ENTROPY_SHIFT + 2;
 654		/* The +2 corresponds to the /4 in the denominator */
 655
 656		do {
 657			unsigned int anfrac = min(pnfrac, pool_size/2);
 658			unsigned int add =
 659				((pool_size - entropy_count)*anfrac*3) >> s;
 660
 661			entropy_count += add;
 662			pnfrac -= anfrac;
 663		} while (unlikely(entropy_count < pool_size-2 && pnfrac));
 664	}
 665
 666	if (unlikely(entropy_count < 0)) {
 667		pr_warn("random: negative entropy/overflow: pool %s count %d\n",
 668			r->name, entropy_count);
 669		WARN_ON(1);
 670		entropy_count = 0;
 671	} else if (entropy_count > pool_size)
 672		entropy_count = pool_size;
 
 
 
 673	if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
 674		goto retry;
 675
 676	r->entropy_total += nbits;
 677	if (!r->initialized && r->entropy_total > 128) {
 678		r->initialized = 1;
 679		r->entropy_total = 0;
 680		if (r == &nonblocking_pool) {
 681			prandom_reseed_late();
 682			process_random_ready_list();
 683			wake_up_all(&urandom_init_wait);
 684			pr_notice("random: %s pool is initialized\n", r->name);
 685		}
 686	}
 687
 688	trace_credit_entropy_bits(r->name, nbits,
 689				  entropy_count >> ENTROPY_SHIFT,
 690				  r->entropy_total, _RET_IP_);
 691
 692	if (r == &input_pool) {
 693		int entropy_bits = entropy_count >> ENTROPY_SHIFT;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 694
 695		/* should we wake readers? */
 696		if (entropy_bits >= random_read_wakeup_bits) {
 
 697			wake_up_interruptible(&random_read_wait);
 698			kill_fasync(&fasync, SIGIO, POLL_IN);
 699		}
 700		/* If the input pool is getting full, send some
 701		 * entropy to the two output pools, flipping back and
 702		 * forth between them, until the output pools are 75%
 703		 * full.
 704		 */
 705		if (entropy_bits > random_write_wakeup_bits &&
 706		    r->initialized &&
 707		    r->entropy_total >= 2*random_read_wakeup_bits) {
 708			static struct entropy_store *last = &blocking_pool;
 709			struct entropy_store *other = &blocking_pool;
 710
 711			if (last == &blocking_pool)
 712				other = &nonblocking_pool;
 713			if (other->entropy_count <=
 714			    3 * other->poolinfo->poolfracbits / 4)
 715				last = other;
 716			if (last->entropy_count <=
 717			    3 * last->poolinfo->poolfracbits / 4) {
 718				schedule_work(&last->push_work);
 719				r->entropy_total = 0;
 720			}
 721		}
 722	}
 723}
 724
 725static void credit_entropy_bits_safe(struct entropy_store *r, int nbits)
 726{
 727	const int nbits_max = (int)(~0U >> (ENTROPY_SHIFT + 1));
 
 
 
 728
 729	/* Cap the value to avoid overflows */
 730	nbits = min(nbits,  nbits_max);
 731	nbits = max(nbits, -nbits_max);
 732
 733	credit_entropy_bits(r, nbits);
 
 734}
 735
 736/*********************************************************************
 737 *
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 738 * Entropy input management
 739 *
 740 *********************************************************************/
 741
 742/* There is one of these per entropy source */
 743struct timer_rand_state {
 744	cycles_t last_time;
 745	long last_delta, last_delta2;
 746	unsigned dont_count_entropy:1;
 747};
 748
 749#define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };
 750
 751/*
 752 * Add device- or boot-specific data to the input and nonblocking
 753 * pools to help initialize them to unique values.
 754 *
 755 * None of this adds any entropy, it is meant to avoid the
 756 * problem of the nonblocking pool having similar initial state
 757 * across largely identical devices.
 758 */
 759void add_device_randomness(const void *buf, unsigned int size)
 760{
 761	unsigned long time = random_get_entropy() ^ jiffies;
 762	unsigned long flags;
 763
 
 
 
 764	trace_add_device_randomness(size, _RET_IP_);
 765	spin_lock_irqsave(&input_pool.lock, flags);
 766	_mix_pool_bytes(&input_pool, buf, size);
 767	_mix_pool_bytes(&input_pool, &time, sizeof(time));
 768	spin_unlock_irqrestore(&input_pool.lock, flags);
 769
 770	spin_lock_irqsave(&nonblocking_pool.lock, flags);
 771	_mix_pool_bytes(&nonblocking_pool, buf, size);
 772	_mix_pool_bytes(&nonblocking_pool, &time, sizeof(time));
 773	spin_unlock_irqrestore(&nonblocking_pool.lock, flags);
 774}
 775EXPORT_SYMBOL(add_device_randomness);
 776
 777static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE;
 778
 779/*
 780 * This function adds entropy to the entropy "pool" by using timing
 781 * delays.  It uses the timer_rand_state structure to make an estimate
 782 * of how many bits of entropy this call has added to the pool.
 783 *
 784 * The number "num" is also added to the pool - it should somehow describe
 785 * the type of event which just happened.  This is currently 0-255 for
 786 * keyboard scan codes, and 256 upwards for interrupts.
 787 *
 788 */
 789static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
 790{
 791	struct entropy_store	*r;
 792	struct {
 793		long jiffies;
 794		unsigned cycles;
 795		unsigned num;
 796	} sample;
 797	long delta, delta2, delta3;
 798
 799	preempt_disable();
 800
 801	sample.jiffies = jiffies;
 802	sample.cycles = random_get_entropy();
 803	sample.num = num;
 804	r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
 805	mix_pool_bytes(r, &sample, sizeof(sample));
 806
 807	/*
 808	 * Calculate number of bits of randomness we probably added.
 809	 * We take into account the first, second and third-order deltas
 810	 * in order to make our estimate.
 811	 */
 
 
 812
 813	if (!state->dont_count_entropy) {
 814		delta = sample.jiffies - state->last_time;
 815		state->last_time = sample.jiffies;
 816
 817		delta2 = delta - state->last_delta;
 818		state->last_delta = delta;
 819
 820		delta3 = delta2 - state->last_delta2;
 821		state->last_delta2 = delta2;
 822
 823		if (delta < 0)
 824			delta = -delta;
 825		if (delta2 < 0)
 826			delta2 = -delta2;
 827		if (delta3 < 0)
 828			delta3 = -delta3;
 829		if (delta > delta2)
 830			delta = delta2;
 831		if (delta > delta3)
 832			delta = delta3;
 833
 834		/*
 835		 * delta is now minimum absolute delta.
 836		 * Round down by 1 bit on general principles,
 837		 * and limit entropy entimate to 12 bits.
 838		 */
 839		credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
 840	}
 841	preempt_enable();
 
 
 
 
 
 
 
 
 
 
 
 
 842}
 843
 844void add_input_randomness(unsigned int type, unsigned int code,
 845				 unsigned int value)
 846{
 847	static unsigned char last_value;
 848
 849	/* ignore autorepeat and the like */
 850	if (value == last_value)
 851		return;
 852
 853	last_value = value;
 854	add_timer_randomness(&input_timer_state,
 855			     (type << 4) ^ code ^ (code >> 4) ^ value);
 856	trace_add_input_randomness(ENTROPY_BITS(&input_pool));
 857}
 858EXPORT_SYMBOL_GPL(add_input_randomness);
 859
 860static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
 861
 862#ifdef ADD_INTERRUPT_BENCH
 863static unsigned long avg_cycles, avg_deviation;
 864
 865#define AVG_SHIFT 8     /* Exponential average factor k=1/256 */
 866#define FIXED_1_2 (1 << (AVG_SHIFT-1))
 867
 868static void add_interrupt_bench(cycles_t start)
 869{
 870        long delta = random_get_entropy() - start;
 871
 872        /* Use a weighted moving average */
 873        delta = delta - ((avg_cycles + FIXED_1_2) >> AVG_SHIFT);
 874        avg_cycles += delta;
 875        /* And average deviation */
 876        delta = abs(delta) - ((avg_deviation + FIXED_1_2) >> AVG_SHIFT);
 877        avg_deviation += delta;
 878}
 879#else
 880#define add_interrupt_bench(x)
 881#endif
 882
 883static __u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
 884{
 885	__u32 *ptr = (__u32 *) regs;
 
 886
 887	if (regs == NULL)
 888		return 0;
 889	if (f->reg_idx >= sizeof(struct pt_regs) / sizeof(__u32))
 890		f->reg_idx = 0;
 891	return *(ptr + f->reg_idx++);
 
 
 
 892}
 893
 894void add_interrupt_randomness(int irq, int irq_flags)
 895{
 896	struct entropy_store	*r;
 897	struct fast_pool	*fast_pool = this_cpu_ptr(&irq_randomness);
 898	struct pt_regs		*regs = get_irq_regs();
 899	unsigned long		now = jiffies;
 900	cycles_t		cycles = random_get_entropy();
 901	__u32			c_high, j_high;
 902	__u64			ip;
 903	unsigned long		seed;
 904	int			credit = 0;
 905
 906	if (cycles == 0)
 907		cycles = get_reg(fast_pool, regs);
 908	c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0;
 909	j_high = (sizeof(now) > 4) ? now >> 32 : 0;
 910	fast_pool->pool[0] ^= cycles ^ j_high ^ irq;
 911	fast_pool->pool[1] ^= now ^ c_high;
 912	ip = regs ? instruction_pointer(regs) : _RET_IP_;
 913	fast_pool->pool[2] ^= ip;
 914	fast_pool->pool[3] ^= (sizeof(ip) > 4) ? ip >> 32 :
 915		get_reg(fast_pool, regs);
 916
 917	fast_mix(fast_pool);
 918	add_interrupt_bench(cycles);
 919
 
 
 
 
 
 
 
 
 
 
 920	if ((fast_pool->count < 64) &&
 921	    !time_after(now, fast_pool->last + HZ))
 922		return;
 923
 924	r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
 925	if (!spin_trylock(&r->lock))
 926		return;
 927
 928	fast_pool->last = now;
 929	__mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool));
 930
 931	/*
 932	 * If we have architectural seed generator, produce a seed and
 933	 * add it to the pool.  For the sake of paranoia don't let the
 934	 * architectural seed generator dominate the input from the
 935	 * interrupt noise.
 936	 */
 937	if (arch_get_random_seed_long(&seed)) {
 938		__mix_pool_bytes(r, &seed, sizeof(seed));
 939		credit = 1;
 940	}
 941	spin_unlock(&r->lock);
 942
 943	fast_pool->count = 0;
 944
 945	/* award one bit for the contents of the fast pool */
 946	credit_entropy_bits(r, credit + 1);
 947}
 
 948
 949#ifdef CONFIG_BLOCK
 950void add_disk_randomness(struct gendisk *disk)
 951{
 952	if (!disk || !disk->random)
 953		return;
 954	/* first major is 1, so we get >= 0x200 here */
 955	add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
 956	trace_add_disk_randomness(disk_devt(disk), ENTROPY_BITS(&input_pool));
 957}
 958EXPORT_SYMBOL_GPL(add_disk_randomness);
 959#endif
 960
 961/*********************************************************************
 962 *
 963 * Entropy extraction routines
 964 *
 965 *********************************************************************/
 966
 967static ssize_t extract_entropy(struct entropy_store *r, void *buf,
 968			       size_t nbytes, int min, int rsvd);
 969
 970/*
 971 * This utility inline function is responsible for transferring entropy
 972 * from the primary pool to the secondary extraction pool. We make
 973 * sure we pull enough for a 'catastrophic reseed'.
 974 */
 975static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes);
 976static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
 977{
 978	if (!r->pull ||
 979	    r->entropy_count >= (nbytes << (ENTROPY_SHIFT + 3)) ||
 980	    r->entropy_count > r->poolinfo->poolfracbits)
 981		return;
 982
 983	if (r->limit == 0 && random_min_urandom_seed) {
 984		unsigned long now = jiffies;
 985
 986		if (time_before(now,
 987				r->last_pulled + random_min_urandom_seed * HZ))
 988			return;
 989		r->last_pulled = now;
 990	}
 991
 992	_xfer_secondary_pool(r, nbytes);
 993}
 994
 995static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
 996{
 997	__u32	tmp[OUTPUT_POOL_WORDS];
 998
 999	/* For /dev/random's pool, always leave two wakeups' worth */
1000	int rsvd_bytes = r->limit ? 0 : random_read_wakeup_bits / 4;
1001	int bytes = nbytes;
1002
1003	/* pull at least as much as a wakeup */
1004	bytes = max_t(int, bytes, random_read_wakeup_bits / 8);
1005	/* but never more than the buffer size */
1006	bytes = min_t(int, bytes, sizeof(tmp));
1007
1008	trace_xfer_secondary_pool(r->name, bytes * 8, nbytes * 8,
1009				  ENTROPY_BITS(r), ENTROPY_BITS(r->pull));
1010	bytes = extract_entropy(r->pull, tmp, bytes,
1011				random_read_wakeup_bits / 8, rsvd_bytes);
1012	mix_pool_bytes(r, tmp, bytes);
1013	credit_entropy_bits(r, bytes*8);
1014}
1015
1016/*
1017 * Used as a workqueue function so that when the input pool is getting
1018 * full, we can "spill over" some entropy to the output pools.  That
1019 * way the output pools can store some of the excess entropy instead
1020 * of letting it go to waste.
1021 */
1022static void push_to_pool(struct work_struct *work)
1023{
1024	struct entropy_store *r = container_of(work, struct entropy_store,
1025					      push_work);
1026	BUG_ON(!r);
1027	_xfer_secondary_pool(r, random_read_wakeup_bits/8);
1028	trace_push_to_pool(r->name, r->entropy_count >> ENTROPY_SHIFT,
1029			   r->pull->entropy_count >> ENTROPY_SHIFT);
1030}
1031
1032/*
1033 * This function decides how many bytes to actually take from the
1034 * given pool, and also debits the entropy count accordingly.
1035 */
1036static size_t account(struct entropy_store *r, size_t nbytes, int min,
1037		      int reserved)
1038{
1039	int entropy_count, orig;
1040	size_t ibytes, nfrac;
1041
1042	BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
1043
1044	/* Can we pull enough? */
1045retry:
1046	entropy_count = orig = ACCESS_ONCE(r->entropy_count);
1047	ibytes = nbytes;
1048	/* If limited, never pull more than available */
1049	if (r->limit) {
1050		int have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
1051
1052		if ((have_bytes -= reserved) < 0)
1053			have_bytes = 0;
1054		ibytes = min_t(size_t, ibytes, have_bytes);
1055	}
1056	if (ibytes < min)
1057		ibytes = 0;
1058
1059	if (unlikely(entropy_count < 0)) {
1060		pr_warn("random: negative entropy count: pool %s count %d\n",
1061			r->name, entropy_count);
1062		WARN_ON(1);
1063		entropy_count = 0;
1064	}
1065	nfrac = ibytes << (ENTROPY_SHIFT + 3);
1066	if ((size_t) entropy_count > nfrac)
1067		entropy_count -= nfrac;
1068	else
1069		entropy_count = 0;
1070
1071	if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
1072		goto retry;
1073
1074	trace_debit_entropy(r->name, 8 * ibytes);
1075	if (ibytes &&
1076	    (r->entropy_count >> ENTROPY_SHIFT) < random_write_wakeup_bits) {
1077		wake_up_interruptible(&random_write_wait);
1078		kill_fasync(&fasync, SIGIO, POLL_OUT);
1079	}
1080
1081	return ibytes;
1082}
1083
1084/*
1085 * This function does the actual extraction for extract_entropy and
1086 * extract_entropy_user.
1087 *
1088 * Note: we assume that .poolwords is a multiple of 16 words.
1089 */
1090static void extract_buf(struct entropy_store *r, __u8 *out)
1091{
1092	int i;
1093	union {
1094		__u32 w[5];
1095		unsigned long l[LONGS(20)];
1096	} hash;
1097	__u32 workspace[SHA_WORKSPACE_WORDS];
1098	unsigned long flags;
1099
1100	/*
1101	 * If we have an architectural hardware random number
1102	 * generator, use it for SHA's initial vector
1103	 */
1104	sha_init(hash.w);
1105	for (i = 0; i < LONGS(20); i++) {
1106		unsigned long v;
1107		if (!arch_get_random_long(&v))
1108			break;
1109		hash.l[i] = v;
1110	}
1111
1112	/* Generate a hash across the pool, 16 words (512 bits) at a time */
1113	spin_lock_irqsave(&r->lock, flags);
1114	for (i = 0; i < r->poolinfo->poolwords; i += 16)
1115		sha_transform(hash.w, (__u8 *)(r->pool + i), workspace);
1116
1117	/*
1118	 * We mix the hash back into the pool to prevent backtracking
1119	 * attacks (where the attacker knows the state of the pool
1120	 * plus the current outputs, and attempts to find previous
1121	 * ouputs), unless the hash function can be inverted. By
1122	 * mixing at least a SHA1 worth of hash data back, we make
1123	 * brute-forcing the feedback as hard as brute-forcing the
1124	 * hash.
1125	 */
1126	__mix_pool_bytes(r, hash.w, sizeof(hash.w));
1127	spin_unlock_irqrestore(&r->lock, flags);
1128
1129	memzero_explicit(workspace, sizeof(workspace));
1130
1131	/*
1132	 * In case the hash function has some recognizable output
1133	 * pattern, we fold it in half. Thus, we always feed back
1134	 * twice as much data as we output.
1135	 */
1136	hash.w[0] ^= hash.w[3];
1137	hash.w[1] ^= hash.w[4];
1138	hash.w[2] ^= rol32(hash.w[2], 16);
1139
1140	memcpy(out, &hash, EXTRACT_SIZE);
1141	memzero_explicit(&hash, sizeof(hash));
1142}
1143
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1144/*
1145 * This function extracts randomness from the "entropy pool", and
1146 * returns it in a buffer.
1147 *
1148 * The min parameter specifies the minimum amount we can pull before
1149 * failing to avoid races that defeat catastrophic reseeding while the
1150 * reserved parameter indicates how much entropy we must leave in the
1151 * pool after each pull to avoid starving other readers.
1152 */
1153static ssize_t extract_entropy(struct entropy_store *r, void *buf,
1154				 size_t nbytes, int min, int reserved)
1155{
1156	ssize_t ret = 0, i;
1157	__u8 tmp[EXTRACT_SIZE];
1158	unsigned long flags;
1159
1160	/* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
1161	if (fips_enabled) {
1162		spin_lock_irqsave(&r->lock, flags);
1163		if (!r->last_data_init) {
1164			r->last_data_init = 1;
1165			spin_unlock_irqrestore(&r->lock, flags);
1166			trace_extract_entropy(r->name, EXTRACT_SIZE,
1167					      ENTROPY_BITS(r), _RET_IP_);
1168			xfer_secondary_pool(r, EXTRACT_SIZE);
1169			extract_buf(r, tmp);
1170			spin_lock_irqsave(&r->lock, flags);
1171			memcpy(r->last_data, tmp, EXTRACT_SIZE);
1172		}
1173		spin_unlock_irqrestore(&r->lock, flags);
1174	}
1175
1176	trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
1177	xfer_secondary_pool(r, nbytes);
1178	nbytes = account(r, nbytes, min, reserved);
1179
1180	while (nbytes) {
1181		extract_buf(r, tmp);
1182
1183		if (fips_enabled) {
1184			spin_lock_irqsave(&r->lock, flags);
1185			if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
1186				panic("Hardware RNG duplicated output!\n");
1187			memcpy(r->last_data, tmp, EXTRACT_SIZE);
1188			spin_unlock_irqrestore(&r->lock, flags);
1189		}
1190		i = min_t(int, nbytes, EXTRACT_SIZE);
1191		memcpy(buf, tmp, i);
1192		nbytes -= i;
1193		buf += i;
1194		ret += i;
1195	}
1196
1197	/* Wipe data just returned from memory */
1198	memzero_explicit(tmp, sizeof(tmp));
1199
1200	return ret;
1201}
1202
1203/*
1204 * This function extracts randomness from the "entropy pool", and
1205 * returns it in a userspace buffer.
1206 */
1207static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
1208				    size_t nbytes)
1209{
1210	ssize_t ret = 0, i;
1211	__u8 tmp[EXTRACT_SIZE];
1212	int large_request = (nbytes > 256);
1213
1214	trace_extract_entropy_user(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
 
 
 
 
 
1215	xfer_secondary_pool(r, nbytes);
1216	nbytes = account(r, nbytes, 0, 0);
1217
1218	while (nbytes) {
1219		if (large_request && need_resched()) {
1220			if (signal_pending(current)) {
1221				if (ret == 0)
1222					ret = -ERESTARTSYS;
1223				break;
1224			}
1225			schedule();
1226		}
1227
1228		extract_buf(r, tmp);
1229		i = min_t(int, nbytes, EXTRACT_SIZE);
1230		if (copy_to_user(buf, tmp, i)) {
1231			ret = -EFAULT;
1232			break;
1233		}
1234
1235		nbytes -= i;
1236		buf += i;
1237		ret += i;
1238	}
1239
1240	/* Wipe data just returned from memory */
1241	memzero_explicit(tmp, sizeof(tmp));
1242
1243	return ret;
1244}
1245
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1246/*
1247 * This function is the exported kernel interface.  It returns some
1248 * number of good random numbers, suitable for key generation, seeding
1249 * TCP sequence numbers, etc.  It does not rely on the hardware random
1250 * number generator.  For random bytes direct from the hardware RNG
1251 * (when available), use get_random_bytes_arch().
 
 
 
1252 */
1253void get_random_bytes(void *buf, int nbytes)
1254{
1255#if DEBUG_RANDOM_BOOT > 0
1256	if (unlikely(nonblocking_pool.initialized == 0))
1257		printk(KERN_NOTICE "random: %pF get_random_bytes called "
1258		       "with %d bits of entropy available\n",
1259		       (void *) _RET_IP_,
1260		       nonblocking_pool.entropy_total);
1261#endif
1262	trace_get_random_bytes(nbytes, _RET_IP_);
1263	extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1264}
1265EXPORT_SYMBOL(get_random_bytes);
1266
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1267/*
1268 * Add a callback function that will be invoked when the nonblocking
1269 * pool is initialised.
1270 *
1271 * returns: 0 if callback is successfully added
1272 *	    -EALREADY if pool is already initialised (callback not called)
1273 *	    -ENOENT if module for callback is not alive
1274 */
1275int add_random_ready_callback(struct random_ready_callback *rdy)
1276{
1277	struct module *owner;
1278	unsigned long flags;
1279	int err = -EALREADY;
1280
1281	if (likely(nonblocking_pool.initialized))
1282		return err;
1283
1284	owner = rdy->owner;
1285	if (!try_module_get(owner))
1286		return -ENOENT;
1287
1288	spin_lock_irqsave(&random_ready_list_lock, flags);
1289	if (nonblocking_pool.initialized)
1290		goto out;
1291
1292	owner = NULL;
1293
1294	list_add(&rdy->list, &random_ready_list);
1295	err = 0;
1296
1297out:
1298	spin_unlock_irqrestore(&random_ready_list_lock, flags);
1299
1300	module_put(owner);
1301
1302	return err;
1303}
1304EXPORT_SYMBOL(add_random_ready_callback);
1305
1306/*
1307 * Delete a previously registered readiness callback function.
1308 */
1309void del_random_ready_callback(struct random_ready_callback *rdy)
1310{
1311	unsigned long flags;
1312	struct module *owner = NULL;
1313
1314	spin_lock_irqsave(&random_ready_list_lock, flags);
1315	if (!list_empty(&rdy->list)) {
1316		list_del_init(&rdy->list);
1317		owner = rdy->owner;
1318	}
1319	spin_unlock_irqrestore(&random_ready_list_lock, flags);
1320
1321	module_put(owner);
1322}
1323EXPORT_SYMBOL(del_random_ready_callback);
1324
1325/*
1326 * This function will use the architecture-specific hardware random
1327 * number generator if it is available.  The arch-specific hw RNG will
1328 * almost certainly be faster than what we can do in software, but it
1329 * is impossible to verify that it is implemented securely (as
1330 * opposed, to, say, the AES encryption of a sequence number using a
1331 * key known by the NSA).  So it's useful if we need the speed, but
1332 * only if we're willing to trust the hardware manufacturer not to
1333 * have put in a back door.
 
 
1334 */
1335void get_random_bytes_arch(void *buf, int nbytes)
1336{
 
1337	char *p = buf;
1338
1339	trace_get_random_bytes_arch(nbytes, _RET_IP_);
1340	while (nbytes) {
1341		unsigned long v;
1342		int chunk = min(nbytes, (int)sizeof(unsigned long));
1343
1344		if (!arch_get_random_long(&v))
1345			break;
1346		
1347		memcpy(p, &v, chunk);
1348		p += chunk;
1349		nbytes -= chunk;
1350	}
1351
1352	if (nbytes)
1353		extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
1354}
1355EXPORT_SYMBOL(get_random_bytes_arch);
1356
1357
1358/*
1359 * init_std_data - initialize pool with system data
1360 *
1361 * @r: pool to initialize
1362 *
1363 * This function clears the pool's entropy count and mixes some system
1364 * data into the pool to prepare it for use. The pool is not cleared
1365 * as that can only decrease the entropy in the pool.
1366 */
1367static void init_std_data(struct entropy_store *r)
1368{
1369	int i;
1370	ktime_t now = ktime_get_real();
1371	unsigned long rv;
1372
1373	r->last_pulled = jiffies;
1374	mix_pool_bytes(r, &now, sizeof(now));
1375	for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {
1376		if (!arch_get_random_seed_long(&rv) &&
1377		    !arch_get_random_long(&rv))
1378			rv = random_get_entropy();
1379		mix_pool_bytes(r, &rv, sizeof(rv));
1380	}
1381	mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
1382}
1383
1384/*
1385 * Note that setup_arch() may call add_device_randomness()
1386 * long before we get here. This allows seeding of the pools
1387 * with some platform dependent data very early in the boot
1388 * process. But it limits our options here. We must use
1389 * statically allocated structures that already have all
1390 * initializations complete at compile time. We should also
1391 * take care not to overwrite the precious per platform data
1392 * we were given.
1393 */
1394static int rand_initialize(void)
1395{
1396	init_std_data(&input_pool);
1397	init_std_data(&blocking_pool);
1398	init_std_data(&nonblocking_pool);
 
 
 
 
 
1399	return 0;
1400}
1401early_initcall(rand_initialize);
1402
1403#ifdef CONFIG_BLOCK
1404void rand_initialize_disk(struct gendisk *disk)
1405{
1406	struct timer_rand_state *state;
1407
1408	/*
1409	 * If kzalloc returns null, we just won't use that entropy
1410	 * source.
1411	 */
1412	state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
1413	if (state) {
1414		state->last_time = INITIAL_JIFFIES;
1415		disk->random = state;
1416	}
1417}
1418#endif
1419
1420static ssize_t
1421_random_read(int nonblock, char __user *buf, size_t nbytes)
1422{
1423	ssize_t n;
1424
1425	if (nbytes == 0)
1426		return 0;
1427
1428	nbytes = min_t(size_t, nbytes, SEC_XFER_SIZE);
1429	while (1) {
1430		n = extract_entropy_user(&blocking_pool, buf, nbytes);
1431		if (n < 0)
1432			return n;
1433		trace_random_read(n*8, (nbytes-n)*8,
1434				  ENTROPY_BITS(&blocking_pool),
1435				  ENTROPY_BITS(&input_pool));
1436		if (n > 0)
1437			return n;
1438
1439		/* Pool is (near) empty.  Maybe wait and retry. */
1440		if (nonblock)
1441			return -EAGAIN;
1442
1443		wait_event_interruptible(random_read_wait,
1444			ENTROPY_BITS(&input_pool) >=
1445			random_read_wakeup_bits);
1446		if (signal_pending(current))
1447			return -ERESTARTSYS;
1448	}
1449}
1450
1451static ssize_t
1452random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1453{
1454	return _random_read(file->f_flags & O_NONBLOCK, buf, nbytes);
1455}
1456
1457static ssize_t
1458urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
1459{
 
 
1460	int ret;
1461
1462	if (unlikely(nonblocking_pool.initialized == 0))
1463		printk_once(KERN_NOTICE "random: %s urandom read "
1464			    "with %d bits of entropy available\n",
1465			    current->comm, nonblocking_pool.entropy_total);
1466
 
 
 
 
 
1467	nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
1468	ret = extract_entropy_user(&nonblocking_pool, buf, nbytes);
1469
1470	trace_urandom_read(8 * nbytes, ENTROPY_BITS(&nonblocking_pool),
1471			   ENTROPY_BITS(&input_pool));
1472	return ret;
1473}
1474
1475static unsigned int
1476random_poll(struct file *file, poll_table * wait)
1477{
1478	unsigned int mask;
1479
1480	poll_wait(file, &random_read_wait, wait);
1481	poll_wait(file, &random_write_wait, wait);
1482	mask = 0;
1483	if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits)
1484		mask |= POLLIN | POLLRDNORM;
1485	if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
1486		mask |= POLLOUT | POLLWRNORM;
1487	return mask;
1488}
1489
1490static int
1491write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
1492{
1493	size_t bytes;
1494	__u32 buf[16];
1495	const char __user *p = buffer;
1496
1497	while (count > 0) {
 
 
1498		bytes = min(count, sizeof(buf));
1499		if (copy_from_user(&buf, p, bytes))
1500			return -EFAULT;
1501
 
 
 
 
 
 
1502		count -= bytes;
1503		p += bytes;
1504
1505		mix_pool_bytes(r, buf, bytes);
1506		cond_resched();
1507	}
1508
1509	return 0;
1510}
1511
1512static ssize_t random_write(struct file *file, const char __user *buffer,
1513			    size_t count, loff_t *ppos)
1514{
1515	size_t ret;
1516
1517	ret = write_pool(&blocking_pool, buffer, count);
1518	if (ret)
1519		return ret;
1520	ret = write_pool(&nonblocking_pool, buffer, count);
1521	if (ret)
1522		return ret;
1523
1524	return (ssize_t)count;
1525}
1526
1527static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
1528{
1529	int size, ent_count;
1530	int __user *p = (int __user *)arg;
1531	int retval;
1532
1533	switch (cmd) {
1534	case RNDGETENTCNT:
1535		/* inherently racy, no point locking */
1536		ent_count = ENTROPY_BITS(&input_pool);
1537		if (put_user(ent_count, p))
1538			return -EFAULT;
1539		return 0;
1540	case RNDADDTOENTCNT:
1541		if (!capable(CAP_SYS_ADMIN))
1542			return -EPERM;
1543		if (get_user(ent_count, p))
1544			return -EFAULT;
1545		credit_entropy_bits_safe(&input_pool, ent_count);
1546		return 0;
1547	case RNDADDENTROPY:
1548		if (!capable(CAP_SYS_ADMIN))
1549			return -EPERM;
1550		if (get_user(ent_count, p++))
1551			return -EFAULT;
1552		if (ent_count < 0)
1553			return -EINVAL;
1554		if (get_user(size, p++))
1555			return -EFAULT;
1556		retval = write_pool(&input_pool, (const char __user *)p,
1557				    size);
1558		if (retval < 0)
1559			return retval;
1560		credit_entropy_bits_safe(&input_pool, ent_count);
1561		return 0;
1562	case RNDZAPENTCNT:
1563	case RNDCLEARPOOL:
1564		/*
1565		 * Clear the entropy pool counters. We no longer clear
1566		 * the entropy pool, as that's silly.
1567		 */
1568		if (!capable(CAP_SYS_ADMIN))
1569			return -EPERM;
1570		input_pool.entropy_count = 0;
1571		nonblocking_pool.entropy_count = 0;
1572		blocking_pool.entropy_count = 0;
1573		return 0;
 
 
 
 
 
 
 
 
1574	default:
1575		return -EINVAL;
1576	}
1577}
1578
1579static int random_fasync(int fd, struct file *filp, int on)
1580{
1581	return fasync_helper(fd, filp, on, &fasync);
1582}
1583
1584const struct file_operations random_fops = {
1585	.read  = random_read,
1586	.write = random_write,
1587	.poll  = random_poll,
1588	.unlocked_ioctl = random_ioctl,
1589	.fasync = random_fasync,
1590	.llseek = noop_llseek,
1591};
1592
1593const struct file_operations urandom_fops = {
1594	.read  = urandom_read,
1595	.write = random_write,
1596	.unlocked_ioctl = random_ioctl,
1597	.fasync = random_fasync,
1598	.llseek = noop_llseek,
1599};
1600
1601SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
1602		unsigned int, flags)
1603{
 
 
1604	if (flags & ~(GRND_NONBLOCK|GRND_RANDOM))
1605		return -EINVAL;
1606
1607	if (count > INT_MAX)
1608		count = INT_MAX;
1609
1610	if (flags & GRND_RANDOM)
1611		return _random_read(flags & GRND_NONBLOCK, buf, count);
1612
1613	if (unlikely(nonblocking_pool.initialized == 0)) {
1614		if (flags & GRND_NONBLOCK)
1615			return -EAGAIN;
1616		wait_event_interruptible(urandom_init_wait,
1617					 nonblocking_pool.initialized);
1618		if (signal_pending(current))
1619			return -ERESTARTSYS;
1620	}
1621	return urandom_read(NULL, buf, count, NULL);
1622}
1623
1624/***************************************************************
1625 * Random UUID interface
1626 *
1627 * Used here for a Boot ID, but can be useful for other kernel
1628 * drivers.
1629 ***************************************************************/
1630
1631/*
1632 * Generate random UUID
1633 */
1634void generate_random_uuid(unsigned char uuid_out[16])
1635{
1636	get_random_bytes(uuid_out, 16);
1637	/* Set UUID version to 4 --- truly random generation */
1638	uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40;
1639	/* Set the UUID variant to DCE */
1640	uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80;
1641}
1642EXPORT_SYMBOL(generate_random_uuid);
1643
1644/********************************************************************
1645 *
1646 * Sysctl interface
1647 *
1648 ********************************************************************/
1649
1650#ifdef CONFIG_SYSCTL
1651
1652#include <linux/sysctl.h>
1653
1654static int min_read_thresh = 8, min_write_thresh;
1655static int max_read_thresh = OUTPUT_POOL_WORDS * 32;
1656static int max_write_thresh = INPUT_POOL_WORDS * 32;
 
1657static char sysctl_bootid[16];
1658
1659/*
1660 * This function is used to return both the bootid UUID, and random
1661 * UUID.  The difference is in whether table->data is NULL; if it is,
1662 * then a new UUID is generated and returned to the user.
1663 *
1664 * If the user accesses this via the proc interface, the UUID will be
1665 * returned as an ASCII string in the standard UUID format; if via the
1666 * sysctl system call, as 16 bytes of binary data.
1667 */
1668static int proc_do_uuid(struct ctl_table *table, int write,
1669			void __user *buffer, size_t *lenp, loff_t *ppos)
1670{
1671	struct ctl_table fake_table;
1672	unsigned char buf[64], tmp_uuid[16], *uuid;
1673
1674	uuid = table->data;
1675	if (!uuid) {
1676		uuid = tmp_uuid;
1677		generate_random_uuid(uuid);
1678	} else {
1679		static DEFINE_SPINLOCK(bootid_spinlock);
1680
1681		spin_lock(&bootid_spinlock);
1682		if (!uuid[8])
1683			generate_random_uuid(uuid);
1684		spin_unlock(&bootid_spinlock);
1685	}
1686
1687	sprintf(buf, "%pU", uuid);
1688
1689	fake_table.data = buf;
1690	fake_table.maxlen = sizeof(buf);
1691
1692	return proc_dostring(&fake_table, write, buffer, lenp, ppos);
1693}
1694
1695/*
1696 * Return entropy available scaled to integral bits
1697 */
1698static int proc_do_entropy(struct ctl_table *table, int write,
1699			   void __user *buffer, size_t *lenp, loff_t *ppos)
1700{
1701	struct ctl_table fake_table;
1702	int entropy_count;
1703
1704	entropy_count = *(int *)table->data >> ENTROPY_SHIFT;
1705
1706	fake_table.data = &entropy_count;
1707	fake_table.maxlen = sizeof(entropy_count);
1708
1709	return proc_dointvec(&fake_table, write, buffer, lenp, ppos);
1710}
1711
1712static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
1713extern struct ctl_table random_table[];
1714struct ctl_table random_table[] = {
1715	{
1716		.procname	= "poolsize",
1717		.data		= &sysctl_poolsize,
1718		.maxlen		= sizeof(int),
1719		.mode		= 0444,
1720		.proc_handler	= proc_dointvec,
1721	},
1722	{
1723		.procname	= "entropy_avail",
1724		.maxlen		= sizeof(int),
1725		.mode		= 0444,
1726		.proc_handler	= proc_do_entropy,
1727		.data		= &input_pool.entropy_count,
1728	},
1729	{
1730		.procname	= "read_wakeup_threshold",
1731		.data		= &random_read_wakeup_bits,
1732		.maxlen		= sizeof(int),
1733		.mode		= 0644,
1734		.proc_handler	= proc_dointvec_minmax,
1735		.extra1		= &min_read_thresh,
1736		.extra2		= &max_read_thresh,
1737	},
1738	{
1739		.procname	= "write_wakeup_threshold",
1740		.data		= &random_write_wakeup_bits,
1741		.maxlen		= sizeof(int),
1742		.mode		= 0644,
1743		.proc_handler	= proc_dointvec_minmax,
1744		.extra1		= &min_write_thresh,
1745		.extra2		= &max_write_thresh,
1746	},
1747	{
1748		.procname	= "urandom_min_reseed_secs",
1749		.data		= &random_min_urandom_seed,
1750		.maxlen		= sizeof(int),
1751		.mode		= 0644,
1752		.proc_handler	= proc_dointvec,
1753	},
1754	{
1755		.procname	= "boot_id",
1756		.data		= &sysctl_bootid,
1757		.maxlen		= 16,
1758		.mode		= 0444,
1759		.proc_handler	= proc_do_uuid,
1760	},
1761	{
1762		.procname	= "uuid",
1763		.maxlen		= 16,
1764		.mode		= 0444,
1765		.proc_handler	= proc_do_uuid,
1766	},
1767#ifdef ADD_INTERRUPT_BENCH
1768	{
1769		.procname	= "add_interrupt_avg_cycles",
1770		.data		= &avg_cycles,
1771		.maxlen		= sizeof(avg_cycles),
1772		.mode		= 0444,
1773		.proc_handler	= proc_doulongvec_minmax,
1774	},
1775	{
1776		.procname	= "add_interrupt_avg_deviation",
1777		.data		= &avg_deviation,
1778		.maxlen		= sizeof(avg_deviation),
1779		.mode		= 0444,
1780		.proc_handler	= proc_doulongvec_minmax,
1781	},
1782#endif
1783	{ }
1784};
1785#endif 	/* CONFIG_SYSCTL */
1786
1787static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
1788
1789int random_int_secret_init(void)
1790{
1791	get_random_bytes(random_int_secret, sizeof(random_int_secret));
1792	return 0;
1793}
 
1794
1795/*
1796 * Get a random word for internal kernel use only. Similar to urandom but
1797 * with the goal of minimal entropy pool depletion. As a result, the random
1798 * value is not cryptographically secure but for several uses the cost of
1799 * depleting entropy is too high
 
 
1800 */
1801static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash);
1802unsigned int get_random_int(void)
 
 
 
1803{
1804	__u32 *hash;
1805	unsigned int ret;
 
 
1806
1807	if (arch_get_random_int(&ret))
 
1808		return ret;
 
 
 
 
 
1809
1810	hash = get_cpu_var(get_random_int_hash);
1811
1812	hash[0] += current->pid + jiffies + random_get_entropy();
1813	md5_transform(hash, random_int_secret);
1814	ret = hash[0];
1815	put_cpu_var(get_random_int_hash);
1816
 
 
 
 
 
 
 
 
1817	return ret;
1818}
1819EXPORT_SYMBOL(get_random_int);
1820
1821/*
1822 * Same as get_random_int(), but returns unsigned long.
1823 */
1824unsigned long get_random_long(void)
1825{
1826	__u32 *hash;
1827	unsigned long ret;
 
 
1828
1829	if (arch_get_random_long(&ret))
1830		return ret;
1831
1832	hash = get_cpu_var(get_random_int_hash);
1833
1834	hash[0] += current->pid + jiffies + random_get_entropy();
1835	md5_transform(hash, random_int_secret);
1836	ret = *(unsigned long *)hash;
1837	put_cpu_var(get_random_int_hash);
1838
 
 
 
 
 
 
 
 
1839	return ret;
1840}
1841EXPORT_SYMBOL(get_random_long);
1842
1843/*
1844 * randomize_range() returns a start address such that
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1845 *
1846 *    [...... <range> .....]
1847 *  start                  end
1848 *
1849 * a <range> with size "len" starting at the return value is inside in the
1850 * area defined by [start, end], but is otherwise randomized.
1851 */
1852unsigned long
1853randomize_range(unsigned long start, unsigned long end, unsigned long len)
1854{
1855	unsigned long range = end - len - start;
 
 
 
1856
1857	if (end <= start + len)
1858		return 0;
1859	return PAGE_ALIGN(get_random_int() % range + start);
 
 
 
 
 
 
1860}
1861
1862/* Interface for in-kernel drivers of true hardware RNGs.
1863 * Those devices may produce endless random bits and will be throttled
1864 * when our pool is full.
1865 */
1866void add_hwgenerator_randomness(const char *buffer, size_t count,
1867				size_t entropy)
1868{
1869	struct entropy_store *poolp = &input_pool;
1870
 
 
 
 
 
1871	/* Suspend writing if we're above the trickle threshold.
1872	 * We'll be woken up again once below random_write_wakeup_thresh,
1873	 * or when the calling thread is about to terminate.
1874	 */
1875	wait_event_interruptible(random_write_wait, kthread_should_stop() ||
1876			ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits);
1877	mix_pool_bytes(poolp, buffer, count);
1878	credit_entropy_bits(poolp, entropy);
1879}
1880EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);